Telephone system



July 2, 1940. w. A. RHODES TELEPHONE SYSTEM Filed Seph'. 24, 1938 F/GZ/2 Sheets-Sheet 1 l ENTOR By W A. RHODES FWV ATTORNEY July 2, 1940.

- INVENTOR By WARHODES MNT M W A TTZENEV Patented July 2, 1940 UNITEDSTATES PATENT OFFICE TELEPHONE SYSTEM wuusm'a. Rhodes, New York, N. r.,assign- 40 Bell Telephone laboratories, Incorporated, New York, N. 2., acorporation of New York Application September :4, 1m, Serial No. 231,411

' 3 Claims. (01. 179-18) This invention relates to telephone systems andparticularly to those in which automatic equipment is used in theestablishment of connections.

The objects of the invention are to obtain greater efliciency andincreased speed in the transmission of telephone designations; tosimplify the operations involved in transferring such designations; andotherwise to improve sys- IO tems of this kind.

Systems have been proposed heretofore in which telephone designations,such as the numbers of subscribers lines or the numbers of trunkcircuits, are transmitted from one point to an- 15 other by means ofcurrents of different frequencies, the frequencies singly or incombination serving to characterize diflerent numerals or othercharacters of the designation. Also, designations have been transferredby means of 20 currents of different polarities and currents ofdifferent magnitudes.

In these prior systems it has been the general practice in transferringdesignations from one point to another to transmit the different digital25 characters in succession.

According to the present invention advantages are secured over theseprior systems by providing mechanism for transferring all .digitalcharacters of the designation simultaneously. To

30 accomplish this purpose, the different digital characters of eachdigital place in the designationare represented by combinations ofalternating current frequencies. Where, for example, a fourdigitdesignation is concerned the different char- 35 acters in the thousandsdigit place are represented by diiferent combinations of four differentfrequencies; the different characters in the hundreds digit place arerepresented by combinations of four other frequencies; and similarly 40the characters of the tens and units places are represented bycombinations of frequencies all of which difier from each other and fromthose of the thousands and hundreds places. After the designation hasbeen registered and the several.

45 frequencies representing the four characters of the designation havebeen selected, these frequencies are then applied all simultaneously tothe transmission line and sent thereover to the r distant oflice. At thedistant oiilce they are received and separated by selective circuits,such as filters, and are caused to operate register relays to registerthe designation thus transmitted.

The foregoing and other features of the invention will be described morefully in detail in the following specification and will also be setforth in the appended claims.

In the drawings Figs. 1 and 2, when taken together, illustrate atelephone exchange system in which interomce connections are establishedby 5 way of trunk lines extending between the different oiilces in thesystem.

Fig. 1 illustrates an originating omce equipped with a register senderfor registering the designation of the called line and for transferringthe registered information over the interomce trunk to the distantterminating oiiice; and

Fig. 2 illustrates a terminating ofiice equipped with a register senderfor receiving the information from the originating office and forcontrolling the switches in the terminating oiiice to complete theconnection.

The system shown in the drawings is abbreviated to a large extent, allparts not essential to an understanding of the invention being omittedfor the sake of clearness and brevity.

The invention is applicable particularly to systems in which the digitalinformation for a call is registered in a common register sender in thecentral office, part of this information being utilized to control theswitches in the oflice to select a trunk extending in the desireddirection, and the remainder of the designation being transferredautomatically over the selected trunk to the distant office where it isreceived and registered in a second common register sender. Here theregistered information is utilized to control the local selectorswitches for completing the connection. Accordingly, the system chosento illustrate the invention is one in which the central ofllces areequipped with automatic switches of the well-known panel type. It willbe understood, however, that other forms of switches to establish theconnections, such as step-by-step switches and cross-bar switches, couldbe used.

Referring to the drawings, a subscriber'sline I00 appears in the contactbank of a line-finder switch F, the line finder F being individual to afirst or district selector switch Sl and also to a sender selectorswitch 8-5. The district selector S-l has access to office selectors,such as the switch 8-2, which in turn have access to outgoing trunksllll extending to distant central oiiices.

The sender selector S-5 has access to a number of common registersenders, one of which is illustrated in part in Fig. 1. The registersender includes a series of digit registers in the form ofsingle-movement step-by-step switches. There are three of these switches(A, B and C) for the 55 ofllce code portion of the designation and fourswitches (TH, H, T and U) for the thousands, hundredsfltens and unitsdigits of the numerical portion of the subscriber's designation. Eachswitch comprises a stepping magnet and a suitable number of brushes andcontact arcs. For example, the first code register A is illustrated byits stepping magnet I02 and a single wiper and contact are I05. Likewisethe other code registers B and C are illustrated by their respectivestepping magnets I03 and I04 and by the wipers I06 and I01. Each ofthese registers may, of course, include other switch wipers. Thethousands register comprises a stepping magnet 08 and three contactwipers I09, H0 and III; the hundreds register H comprises a steppingmagnet H2 and three switch wipers II3, I I4 and H5. Similarly the tensand units registers comprise stepping magnets II6 and II! and thecorresponding switch wipers H8, H9, I20 and wipers I2I, I22, I23.

The code registers A, B and C serve to control the selective operationof the district and ofiice selectors SI and S-2 to seize a desiredoutgoing trunk II". The four numerical registers register the number ofthe wanted subscriber's line and serve either one of two purposes. Ifthe call is a local one, these registers control the local incoming andfinal'selectors to complete the connection to the called line. Theincoming and final selectors of the local office are not shown. Theywould, of course, be provided and would correspond to the switches S3and 8-4 of the ofiice shown in Fig. 2. 0n the other hand, if the callorignating in the office shown in Fig. 1 is for a subscriber in adistant ofiice, these registers determine the transmission of a code ofalternating current frequencies over the selected trunk to the distantoifice where the number is received in a corresponding sender.

The combination of frequencies for transmitting the thousands digit isobtained from the four alternating current generators I29, I30, I3I andI32. The codes for the hundreds digits are obtained from the fourgenerators I33, I34, I35 and I36. Similarly, the codes for the tensdigits and the units digits are obtained from the generators I31, I38,I39, I40 and HI, I42, I43, I44. These generators produce currents ofsixteen different frequencies, and they are selected in differentcombinations by the brushes of the numerical registers. They control theoutput circuits of the space-discharge tubes I45, I46, I41, I48, I49,I50, I5I and I52 to transmit over the line to the distant ofiice asingle impulse of current comprising all of the different frequencycomponents representing the particular numerical designation identifyingthe called subscribers line.

During the time the calling subscriber is dialing the digits of thewanted designation his line is associated successively with the code andnumerical registers of the sender by means of a register control switchRC including the magnet I24 and the switch wipers I25, I26 and I21.

The register sender also includes numerous relays and a sequence switchI28 for switching the circuits of the sender from one stage of operationto another.

The terminating ofilce illustrated in Fig. 2 includes incoming'and finalselector switches S3 and 8-4 for extending the incoming connections tothe called subscribers lines, such as line 200. The switches S3 and S4are controlled by common register senders, one of which is illustratedin part. These register senders are selected by a sender selector switch8-6 which is individual to the incoming selector S3.

The incoming register sender comprises a frequency selective receivingcircuit 20I, including amplifying means 202 and groups of tunedselective filters or other resonant devices. There are four groups offilters 203, 204, 205 and 206, one for each of the digital places in thenumerical designation of a called line. Associated with the thousandsgroup of filters 203 is a corresponding group of register relays 201,including four relays. These relays respond to the currents passing thefilters 208, 209, 2I0 and 2H and operate to register the value of thethousands digit. In a similar manner, groups of register relays 2I2,2I3, and 2 are provided for the three remaining digital places.

The incoming register sender also includes numerous control relays and asequence switch 2 I5 for controlling the switching operations. Thesender further includes a series of counting relays 2I6 which cooperatewith the registers to control the selective operation of the incomingand final switches S3 and S-4.

As noted above, many details have been omitted in the drawings, such asthe structure and .circuits of the selective switches, the manner inwhich the sender selectors seize idle senders in response to incomingcalls, the manner in which the sender receives and registers thesuccessive digits transmitted by the calling subscribers dial, themanner in which the code registers function to control the operation ofthe selector switches to seize trunks to the desired oflices, the mannerin which the numerical registers control the selective switches tocomplete connections to called lines, and in fact numerous other detailsof operation. For a better understanding of these details, reference maybe had to many patents in the prior art relating to systems of thisgeneral character and in particular to the following patents: Stearn etal., No. 1,395,977 of November 1, 1921; Steam, No. 1,505,171 of August19, 1924; and Raymond et al., No. 1,862,549 of June 14, 1932.

The operation of the system will now be described in detail. Assume forthis purpose that the subscriber of line I00 wishes to call thesubscriber of line 200 in the distant office and that the designation ofline 200 is CHEF-5678. When the calling subscriber removes his receiver,the line finder F finds the calling line, and the sender selector switchS5 is set in motion to select an idle register sender. Thereupon apulsing circuit is established from battery through the left winding ofrelay I53 over the contacts of switch S5, through the contacts ofsequence switch spring I54 of the sequence switch associated with thedistrict selector switch SI, through the brush of the line finder F,thence over the line I00 and returning through the line-finder switchsequence switch spring I55, contacts of sender selector S5 through theright winding of relay I53, normal contact of wiper I25 through thesecondary winding of the tone coil I56 to ground. The calling subscriberhears the dial tone and proceeds to operate his dial I51 to transmitfirst the three oflice digits and then the four numerical digits.

When the pulse relay I53 first operated, it closed an obvious circuitfor slow-release relay I58. On the first release of relay I53 for thefirst impulse of the first digit, slow-release relay I59 is operated ina circuit through the contacts of relays I58 and I53. Also a circuit isclosed from ground through the right back contact of relay I53, outerright contact 01! relay I58, brush I21 (position 1) through the windingof register stepping magnet I02 to battery. Magnet I02 energizes, and,when the impulse ceases and relay I53 reoperates, the magnet againdeenergizes and advances the brush I and other brushes of the sameswitch to the first position contacts. For each succeeding impulse inthe series the wiper I05 takes an additional step, finally coming torest in a position corresponding tothe first code digit. When relay I59operated it closed an obvious circuit for the stepping magnet I24 of thecontrol switch RC. At the end of the first series of impulses relay I53attracts its armatures, and, after an interval, relay I59 releases.Thereupon the magnet I24 releases and steps the brushes I25, I26 and I21to the next position.

When the next series of impulses are received the stepping circuit isextended over the second position contact of brush I21 to the steppingmagnet I03, and magnet I03 advances the brush I06 of the second registerin response to these impulses. At the end of the second series ofimpulses the relay I59 again releases magnet I24, and the switch RCsteps to the third position.

Next the third oiiice code impulses are transmitted, and the magnet I04advances the brush I01 of the third code register to the correspondingposition.

In a similar manner the four numerical digits are received andregistered on the switches TH, H, T and U, the switch RC advancing fromone position to another between successive-series of impulses.

Following the registration of the designation the sender sequence switchI28 is advanced through successive positions where the fundamentalcircuit is completed for controlling the selective operations of thedistrict and ofllce selectors SI and 8-2 to seize an idle trunkextending to an incoming selector. The fundamental circuit, which ispartially illustrated, may

. be traced from conductor I60 in the district selector over the brushof selector switch S--5, conductor I6I, through the inner right backcontact of relay I62, contacts of sender sequence switch spring I63, thestepping relay I64, contacts of sequence switch spring I65, inner leftback contact of relay I62, conductor I66, contacts of selector switch8-5 to the conductor I61. These selective operations are controlled inthe well-known manner by the setting of the three code registers A, Band C.

Had the calling subscriber made a local call, that is, a call foranother line in his exchange,

the numerical registers TH, H, T and U would now .control the incomingand final switches, not

shown, in the local oflice to complete the connection. The assumptionis, however, that the calling subscriber wishes to converse with thesubscriber of line 200 in the distant omce. Accordingly, the districtand oflice selectors SI and 8-2 have selected an idle trunk IOIextending to the distant oflice and there terminating in the incomingselector switch S3. The extension of the call to the incoming selectorS3 causes the sender selector SB to seize an idle sender in a mannersimilar to the operation of the sender selector S-,5 in response to theextension of the call to the district selector S-I.

Since the call is one for a distant omce, a class relay I68 is operatedin the originating sender to identify the class of the call being made.This relay is operated in the well-known manner under the control of thecode registers A, B and C. With the class relay I68 operated and thesender sequence switch- I28 advanced to the position it assumes upon theextension of the connection to the distant ofilce, a circuit is closedfrom battery through the winding of relay I69, through the closedcontacts of sequence switch spring I10, contact of class relay I68 toground. As soon thereafter as the incoming sender is seized at thedistant omce a circuit is completed from battery through the coil 2",contacts of switch S8, contacts of spring 2I8 of a sequence switchassociated with the selector S3, thence over trunk conductor I1I,brushes of switches S2 and SI, closed contacts of sequence switch springI12, contact of switch S5, conductor I66, contact of relay I69,polarized relay I13, conductor I6I, contacts of switch S5, closedcontacts of sequence switch spring I14, brushes of switches SI and 8-2,trunk conductor I15, contacts of sequence switch spring 2I9, contacts ofswitch S-6 through coil 220 to ground. The current flowing in thiscircuit is in the proper direction to operate the polarized relay I13.The operation of relay I13 is a signal to the originating sender to theeffect that the sender at the distant office has been seized and is nowin readiness to receive the single composite frequency signalrepresenting the digits of the called subscriber's number.

When the polar relay I13 operates, it closes a circuit from ground tothe left contact of relay I16, closed contact of relay I13 through thewinding of relay I62 to battery. Relay I62 operates and connects thesecondary winding of the frequency sending transformer I11 to theoutgoing trunk. Relay I62 remains operated for a short interval which ismeasured by the time that slow-operating relay I16 requires to attractits armatures, relay I16 having its circuit closed as soon as relay I62operates. While the secondary oi the tone transformer I11 is connectedto the outgoing trunk, the primary winding is connected to the outputcircuits of the space-discharge tubes I45 to I52, inclusive. The circuitfor this purpose may be traced from battery through the primary ,windingof transformer I11, contacts of sequence switch spring I18 and thence tothe plate electrodes of the several space-discharge tubes. At this timethe filaments of the several tubes are energized in a circuit frombattery through the closed contact of sequence switch spring I19 thencein parallel through the several filaments to ground.

Since the numerical portion of the subscribers designation was assumedto be 5678 the brushes IIO-and III of the thousands register arestanding on the fifth position terminals I80 and I8I the brushes H4 andH5 of the hundreds register are standing on the sixth position terminalsI82 and I83; the brushes H9 and I20 of the tens register are standing onthe seventh position terminals I84 and 185; and the brushes I22 and I23of the units register are standing on the eighth position terminals I86and I81. The terminals I80 to I81, inclusive, are connected respectivelyto the generators I29, I30, I33, I35, I31, I40, I42 and I 43. Hence, thecurrent flowing in the primary winding of transformer I11 is made up ofa plurality of alternating current components which are produced in theanode circuits of the space-discharge tubes I45 to I52, inclusive, underthe control of the generators I29, I30, I33, I35,

'I31, I40, I42 and I43. These alternating ourrent components of thecomposite current flowing in the transformer I11 correspond in frequencyto the frequencies of said generators. These components are inducedsimultaneously in the secondary winding of transformer I11 and aretransmitted as a single composite impulse over the trunk line IM to thedistant office where it is delivered to the receiving circuit 20I. Thiscomposite signal continues to fiow for the brief interval required forthe operation of the slowacting relay I16. When this relay operates atthe end of the measured interval, it looks to the sequence switch springI88 and opens the circuit of relay I82. Relay I02 releases immediately,opening the secondary winding of the transformer I 11 and terminatingthe transmission of the composite impulse. Relay I16 in operating alsoserves to advance the sender sequence switch I28 into a succeedingcircuit controlling position. The circuit for this purpose may be tracedfrom ground through the left back contact of relay I 62, right frontcontact of relay I18, sequence switch spring I89 through the winding ofthe sequence switch magnet I28 to battery.

At the distant office the composite impulse flowing in the receivingcircuit 20I may be amplifled if necessary by an amplifier 202 which thendelivers the amplified currents to the input circuits of the severalgroups of tuned filters 203, 204, 205, 206. Since the first digit (5) ofthe number that is being transmitted is represented by the frequenciesofgenerators I29 and I30, these two frequency components are passedselectively by the filters 208 and 209, respectively, and are not passedby any of the other filters. The currents passing the filters 208 and209 cause the operation of register relays 22I and 222. These relayslock in holding circuits traceable through their upper windings andcontacts over holding conductor 223 to ground through the closedcontacts of spring 224 of sequence switch 2I5. In a similar manner thecomponents corresponding to generators I33 and I35, representing thesecond digit (6), are passed by filters 225 and 220 of the second group204, causing the operation of corresponding register relays of the group2I2. Likewise the components from generators I31 and I40 for the thirddigit (7) and the components from generators I42 and I43 for the fourthdigit (8) are passed by filters 221 and 228 of the third group 205, andby filters 228 and 230 of the fourth group 208, causing in turn theoperation of corresponding register relays of the groups 2I3 and 2I4,respectively.

In this manner the entire numerical designation for the calledsubscriber's line 200 is transmitted from the originating offlce to theterminating office by a single composite impulse of current whichrequires only a brief interval of time. Following the receipt of thecomposite impulse and the selective operation of the relay registers201, 2I2, 2I3 and 2I4, the sequence switch 2I5 is advanced in thewell-known manner to succeeding positions where the fundamental circuitis established for controlling the selective operations of the incomingand final switches S-3 and S4 in accordance with the settings of theseregisters. The fundamental circuit is illustrated briefly and may betraced from conductor 23I, over a brush of sender selector S8, throughthe sequence switch spring 232, through the winding of the steppingrelay 233, sequence switch spring 234 thence through a brush of selectorS6 to the conductor 235. During the first, or brush selecting operationfor the switch 8-3 the stepping relay 233 operates the count- 1 ingrelays 2l6 in the well-known manner, the number of counting relays beingoperated depending upon the particular relays of the register 201 thatare operated. The drawings show the connection between the contacts ofthe register relays 201 to the contacts of the counting relays 2I6. Withthe sequence switch 2I5 in the position for the brush selectingoperation for switch S3, its springs 236, 231 and 238 are closed toconnect ground to armatures of the relays of the register 201.Accordingly, a circuit is completed from ground through sequence switchspring 236, front contact of register relay 22I, front contact ofregister relay 222, conductor 239 to the corresponding one of thecounting relays of the chain 2I6. In the well-known manner thisconnection determines the extent of the brush selecting operation forthe switch S3 Similarly the succeeding selective operations for theswitches 8-3, 8-4 are controlled in turn by the register relays 2I2, 2I3 and 2I4 and the counting relays 2I6.

Following the selection of the called subscribers line 200, ringingcurrent is applied to signal the subscriber.

The senders in the originating and terminating offices may be releasedat any suitable time after they have completed their functions. In therelease of the sender in the originating ofllce, the sequence switchI28, the control switch BC, the register switches, and the variouscontrolling relays are restored to normal. The release of the controlswitch RC is controlled by the wiper I28 which completes aself-interrupting circuit for the stepping magnet I24 through a closedcontact of the slow-releasing relay I58. Similarly the release of theseveral registers A, B and 0, TH, H, T and U, is controlled by restoringcircuits closed through wipers of these respective switches.

It should be understood that this invention is not limited to theparticular embodiment disclosed herein. For instance, other types ofautomatic switches may be employed in establishing the connections, andin fact the designations may be transmitted to operators positions wherethey are displayed on indicating devices. Also various types ofdesignation registers may be used and various types of frequencyselective devices for separating the components of the current signals.Moreover, the transmission of the designations in accordance with thisinvention should not be limited to designations of any particular kindnor to any number of current components for the representation of thedifferent characters. The frequencies to be used for the severalcomponents may be chosen to suit the particular conditions involved. Itwill be noted that specific frequency values are indicated on thefilters 203, 204, 205, 208, but these values are, of course, merelyillustrative.

What is claimed is:

1. In a communication system in which subscribers are assigneddesignations each compris-- ing a plurality of separate characters, thecombination of a transmission line, a plurality of sources of currentsof different characters for representing the separate characters of anysubscriber's designation, means for transmitting over said linesimultaneously the currents corresponding to the several characters ofany desired designation, and means responsive to the currentstransmitted.

2. In a telephone system in which the designations have a plurality ofcharacters, different designations comprising different combinations ofcharacters, sources of current of different frequencies, differentcharacters of said designations being represented by differentfrequencies, a telephone line, and means for transmitting any telephonedesignation by applying to said line simultaneously currents of thefrequencies representing all of the characters of such designation.

3. In a telephone system in which the designations have a plurality ofdigital places, the characters in each digital place varying with, thedifferent designations, sources of alternating current of a plurality'of different frequencies, the,

different characters of each digital place being distinguished fromother characters of the same place and from the characters of otherplaces by different combinations of said frequencies, a line, and meansfor transmitting all digits of any particular designation over said linetogether by applying simultaneously to the line currents of allfrequencies representing all of the characters in the several digitalplaces of said designation.

4. In a communication system in which each designation has a pluralityof characters, different designations comprising different combinationsof characters, sources of current of different frequencies, differentcharacters of said designations being represented by differentfrequencies, a line, means for transmitting any designation over saidline by applying thereto simultaneously currents of the frequenciesrepresenting all-of the characters of such designation, register meansfor registering the characters of the designation transmitted over saidline, and automatic switches controlled by said registers forestablishing a connection.

5. In a telephone system in which each telephone designation comprises aplurality of characters, each character of a designation beingrepresented by a different frequency of alternating current, means forproducing the different frequency currents necessary to represent thedifferent designations, a telephone line, means for sending over saidline a single composite current signal comprising the frequencycomponents representing all of the characters of a desired telephonedesignation, transmitted signal and for utilizing the same to establisha telephone connection.

6. In a telephone system in which each telephone designation has aplurality of characters, different designations comprising differentcombinations of characters, sources of current of different frequencies,each of the characters of a designation beingrepresented by a diflerentcombination of said frequencies, a transmission line, means for sendingover said line a single composite current signal comprising all thefrequencies representing a desired designation, receiving and means forreceiving the means responsive to the transmitted signal for separatingthe frequency currents representing the different characters of thedesignation, automatic switches, and means responsive to the separatedfrequency currents for selectively controlling the operation of saidautomatic switches.

7. In a telephone system in which each subscribers designation isrepresented by a plurality of digital characters, a plurality of sourcesof current of different frequencies, the characters in each digitalplace of a designation being represented by different combinations ofsaid frequencies, an oifice having registers therein for registering adesired designation, a distant omce, a line extending between saidofiices, means controlled by said registers for selecting the frequencysources representing the desired designation and for transmitting oversaid line a single impulse of current including the frequency componentscorresponding to all the characters of said designation, a plurality ofdigital registers at said distant ofilce, tuned selecting devices atsaid distant office for receiving said impulse of current and forselectively separating the difierent frequency components to set saidregisters in accordance with the characters of the transmitteddesignation, and automatic switches in said dis tant omce controlled bysaid registers for estab= lishing a connection corresponding to thetransmitted designation,

8. In a telephone system in which subscribers designations .have aplurality of digital places, each place represented by any one of aplurality of numerals, a plurality of sources of current of differentfrequencies, each of the numerals in each of said digital places beingrepresented by a different combination of said frequencies, a telephoneoflice having automatic switches, reglsters in said ofilce forregistering a desired desig= nation transmitted thereto by a callingsubscriber, a distant ofiice, a line extending between said oflices,means for controlling the selective operation of said switches inaccordance with the setting of said registers to extend the connectionover said line to said distant oiilce, means controlled by saidregisters for selecting the frequency sources representing thedesignation of the wanted subscriber in said distant ofiice and fortransmitting over said line a single impulse of current including thefrequency components corresponding to all of the numerals of thedesignation oi the desired line, digital registers in said distantofllce, tuned selecting devices at said distant office for receivingsaid impulse of cur- .WILUIAM A. RHODES.

